fix(arreflect): full multi-level ptr deref in all builder loops, add tests

Replace single-level if-isPtr-Elem() with for-Kind-Ptr-deref loop in:
buildPrimitiveArray, iterSlice, buildStructArray, buildMapArray,
buildFixedSizeListArray — matching buildDictionaryArray/buildListLikeArray.
Add multi_level_pointer_int32 and multi_level_pointer_struct tests.

Author: zeroshade

arrow/array/arreflect/reflect_go_to_arrow.go

@@ -98,11 +98,16 @@ func buildPrimitiveArray(vals reflect.Value, mem memory.Allocator) (arrow.Array,
 	for i := 0; i < vals.Len(); i++ {
 		v := vals.Index(i)
 		if isPtr {
-			if v.IsNil() {
-				b.AppendNull()
+			for v.Kind() == reflect.Ptr {
+				if v.IsNil() {
+					b.AppendNull()
+					break
+				}
+				v = v.Elem()
+			}
+			if v.Kind() == reflect.Ptr {
 				continue
 			}
-			v = v.Elem()
 		}
 		if err := appendPrimitiveValue(b, v, dt); err != nil {
 			return nil, err
@@ -207,11 +212,16 @@ func iterSlice(vals reflect.Value, isPtr bool, appendNull func(), appendVal func
 	for i := 0; i < vals.Len(); i++ {
 		v := vals.Index(i)
 		if isPtr {
-			if v.IsNil() {
-				appendNull()
+			for v.Kind() == reflect.Ptr {
+				if v.IsNil() {
+					appendNull()
+					break
+				}
+				v = v.Elem()
+			}
+			if v.Kind() == reflect.Ptr {
 				continue
 			}
-			v = v.Elem()
 		}
 		if err := appendVal(v); err != nil {
 			return err
@@ -421,11 +431,16 @@ func buildStructArray(vals reflect.Value, mem memory.Allocator) (arrow.Array, er
 	for i := 0; i < vals.Len(); i++ {
 		v := vals.Index(i)
 		if isPtr {
-			if v.IsNil() {
-				sb.AppendNull()
+			for v.Kind() == reflect.Ptr {
+				if v.IsNil() {
+					sb.AppendNull()
+					break
+				}
+				v = v.Elem()
+			}
+			if v.Kind() == reflect.Ptr {
 				continue
 			}
-			v = v.Elem()
 		}
 		sb.Append(true)
 		for fi, fm := range fields {
@@ -787,11 +802,16 @@ func buildMapArray(vals reflect.Value, mem memory.Allocator) (arrow.Array, error
 	for i := 0; i < vals.Len(); i++ {
 		m := vals.Index(i)
 		if isPtr {
-			if m.IsNil() {
-				mb.AppendNull()
+			for m.Kind() == reflect.Ptr {
+				if m.IsNil() {
+					mb.AppendNull()
+					break
+				}
+				m = m.Elem()
+			}
+			if m.Kind() == reflect.Ptr {
 				continue
 			}
-			m = m.Elem()
 		}
 		if m.IsNil() {
 			mb.AppendNull()
@@ -841,11 +861,16 @@ func buildFixedSizeListArray(vals reflect.Value, mem memory.Allocator) (arrow.Ar
 	for i := 0; i < vals.Len(); i++ {
 		elem := vals.Index(i)
 		if isPtr {
-			if elem.IsNil() {
-				fb.AppendNull()
+			for elem.Kind() == reflect.Ptr {
+				if elem.IsNil() {
+					fb.AppendNull()
+					break
+				}
+				elem = elem.Elem()
+			}
+			if elem.Kind() == reflect.Ptr {
 				continue
 			}
-			elem = elem.Elem()
 		}
 		fb.Append(true)
 		for j := 0; j < int(n); j++ {

arrow/array/arreflect/reflect_go_to_arrow_test.go

@@ -48,16 +48,19 @@ func TestBuildPrimitiveArray(t *testing.T) {
 		}
 	})
 
-	t.Run("string", func(t *testing.T) {
-		vals := []string{"hello", "world", "foo"}
+	t.Run("multi_level_pointer_int32", func(t *testing.T) {
+		v := int32(42)
+		pv := &v
+		var nilPv *int32
+		vals := []**int32{&pv, &nilPv, &pv}
 		arr, err := buildArray(reflect.ValueOf(vals), tagOpts{}, mem)
 		require.NoError(t, err)
 		defer arr.Release()
-		assert.Equal(t, arrow.STRING, arr.DataType().ID())
-		typed := arr.(*array.String)
-		for i, want := range vals {
-			assert.Equal(t, want, typed.Value(i), "[%d] value mismatch", i)
-		}
+		assert.Equal(t, 3, arr.Len())
+		assert.False(t, arr.IsNull(0))
+		assert.True(t, arr.IsNull(1))
+		assert.False(t, arr.IsNull(2))
+		assert.Equal(t, int32(42), arr.(*array.Int32).Value(0))
 	})
 
 	t.Run("pointer_with_null", func(t *testing.T) {
@@ -312,6 +315,23 @@ func TestBuildStructArray(t *testing.T) {
 		assert.Equal(t, int32(10), bxArr.Value(0))
 		assert.Equal(t, int32(20), bxArr.Value(1))
 	})
+
+	t.Run("multi_level_pointer_struct", func(t *testing.T) {
+		type S struct {
+			X int32
+		}
+		s := S{X: 99}
+		ps := &s
+		var nilPs *S
+		vals := []**S{&ps, &nilPs, &ps}
+		arr, err := buildArray(reflect.ValueOf(vals), tagOpts{}, mem)
+		require.NoError(t, err)
+		defer arr.Release()
+		assert.Equal(t, 3, arr.Len())
+		assert.False(t, arr.IsNull(0))
+		assert.True(t, arr.IsNull(1))
+		assert.False(t, arr.IsNull(2))
+	})
 }
 
 func TestBuildListArray(t *testing.T) {